Most recently Refrigeration and Air Conditioning - Mechanical Engineering Objective type questions and answers

41.    Absorption system normally uses the following refrigerant
(a) Freon-11
(b) Freon-22
(c) C02
(d) S02
(e) ammonia.
Ans: e

42. One of the purposes of sub-cooling the liquid refrigerant is to
(a)    reduce compressor overheating
(b)    reduce compressor discharge tempera-ture
(c)    increase cooling effect
(d)    ensure that only liquid and not the vapour enters the expansion (throttling) valve
(e)    none of the above.
Ans: d

43.   The value of COP in vapour compression cycle is usually
(a)    always less than unity
(b)    always more than unity
(c)    equal to unity
(d)    any one of the above
(e)    none of the above.
Ans: b

44.  In a refrigeration system, heat absorbed in comparison to heat rejected is
(a)     more 
(b)     less
(c)    same
(d)    more for small capacity and less for high capacity
(e)    less for small capacity and more for high capacity.
Ans: b

45.  Condensing temperature in a refrigerator is the temperature
(a)    of cooling medium
(b)    of freezing zone
(c)    of evaporator
(d)    at which refrigerant gas becomes liquid
(e)    condensing temperature of ice.
Ans: d

46. Formation of frost on evaporator in refrigerator
(a)    results in loss of heat due to poor heat transfer
(b)    increases heat transfer rate
(c)    is immaterial
(d)    can be avoided by proper design
(e)    decreases compressor power.
Ans: a

47.  In refrigerators, the temperature difference between the evaporating refrigerant and the medium being cooled should be
(a)    high, of the order of 25°
(b)    as low as possible (3 to 11°C)
(c)    zero 
(d)     any value
(e)     none of the above.
Ans: b

48.    In a flooded evaporator refrigerator, an accumulator at suction of compressor is used to
(a)    collect liquid refrigerant and prevent it from going to compressor
(b)    detect liquid in vapour
(c)    superheat the vapour
(d)    collect vapours
(e)    increase refrigeration effect.
Ans: a

49.    Accumulators should have adequate volume to store refrigerant charge at least
(a)     10% 
(b)     25%
(c)     50% 
(d)     75%
(e)     100%.
Ans: c

50.    At lower temperatures and pressures, the latent heat of vaporisation of a refrigerant
(a)     decreases 
(b)     increases
(c)    remains same
(d)    depends on other factors
(e)    none of the above.
Ans: b

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